The invention relates to electronic ride control systems for work vehicles. More particularly, it relates to ride control systems for agricultural tractors using the position of a front suspension as feedback to the electronic ride control system to reduce vehicle pitching and to increase front wheel ground contact time.
The motion of any body can be fully described in three dimensions, by defining three orthogonal axes, surge (longitudinal), sway (lateral), heave (vertical)) and the angular rotation about those axes (roll, pitch, yaw).
Operator ride, comfort, safety and vehicle motion depend on the combined effect of, the excursions and frequency distribution of each degree of freedom, and the interaction of each significant mass/elastic element in the system (cab, seat, suspension, etc). This varies significantly from one operating condition to another, and can be particularly complex when in work mode. Tasks such as plowing may require compensation in all six degrees for full operator isolation.
Even when roading, uncomfortable pitch, heave and shock excursions can build up, to the extent that the front wheels can lose ground contact for substantial periods of time, causing a significant loss of yaw control. This motion results from the vehicle""s dynamic response to externally applied terrain inputs and other disturbances such as those induced by hitch (implement) motion, suspension and wheel eccentricities etc. Unintended cross talk (interaction) between otherwise independently controlled subsystems (e.g. suspension and hitch control) can additionally exacerbate this problem.
In addition to operator comfort and controllability, safety becomes a concern at the higher (20-50 kph) speeds.
Fortunately, the motion of a tractor/implement combination, on the road, is predominately in pitch, heave and to a lesser extent surge (the vertical plane), as is the effect of hitch and front suspension movement, and this is the focus of this invention.
One of the primary causes of this unwanted motion in agricultural tractors is due to overhanging loads that extend outward and behind. These overhanging loads, such as implements coupled to the vehicle are attached to tractors by three-point hitches, a common hitch arrangement used to couple implements to tractors. These hitches have one or more hydraulic actuators, such as hydraulic cylinders, that lift the hitch thereby holding the hitch-mounted implement outward away from the rear of the tractor above the ground. These hitch-mounted implements may be quite heavy, and as large cantilevered loads tend to pivot the tractor about its rear wheels in a manner that lifts the front end of the tractor in the air.
Electronic ride control systems, such as those described in U.S. Pat. Nos. 5,897,287, 5,890,870, and 6,196,327 improve the ride by decoupling the inertia of the hitch and hitch-mounted implement from the chassis of the tractor itself. They do this by dynamically raising and lowering the implement in response to signals received from load pins and hitch position sensors.
Current electronic ride control systems, however, are limited in that they can only sense a limited number of motions of the vehicle. In particular, they sense the loads and positions of components at the rear of the vehicle and not at the front of the vehicle. What is needed therefore is an electronic ride control system that combines the traditional control using hitch height and hitch load with additional position information provided by an additional vehicle position sensor.
It is an object of this invention to provide such a system.
This system includes an enhancement to existing control strategies and an extension of existing system""s capability due to the use of sensor inputs from the additional sub-systems (controlled elements) that may be fitted to the vehicle. They provide the potential for implementing a better set of control algorithms and strategies, based on the equipment fit and knowledge of the vehicle dynamics.
This invention provides additional and immediate functionality, to improve operator selectable ride quality features and, obviate potentially adverse cross talk (interaction) between otherwise independently controlled subsystems (e.g. front suspension and ride control).
Secondary advantages include, lower shock loads to the hitch implement structure and couplings, lower operator fatigue, improved controllability (front wheels on ground longer), enhanced safety, higher permissible road speeds (important in Europe), and alleviation of xe2x80x98porpoisingxe2x80x99, etc.
In accordance with a first embodiment of the invention, a tractor having a ride control system that controls tractor pitching is provided, including a chassis; an engine mounted on the chassis; a hydraulic pump coupled to and driven by the engine to provide a flow of pressurized hydraulic fluid; a front suspension including two front wheels disposed on opposing sides of the chassis and supported by at least one front suspension hydraulic actuator configured to raise and lower the two front wheels with respect to the chassis; a front suspension sensor coupled to the front suspension to generate a signal indicative of the position of the front suspension with respect to the chassis; two rear wheels coupled to the chassis to rotate with respect thereto and drive the vehicle over the ground; a multi-point hitch coupled to the rear of the chassis and configured to be coupled to an overhanging load extending from the rear of the chassis; a hitch position sensor coupled to the hitch to provide a signal indicative of an elevation of the hitch with respect to the chassis; a hitch hydraulic actuator coupled to the hitch to raise and lower the hitch with respect to the chassis; at least one load sensor coupled to the chassis to provide a signal indicative of a load on the hitch; at least one electrically actuated hitch control valve coupled to and between the pump and the hitch hydraulic actuator to regulate the flow of pressurized hydraulic fluid to the hitch hydraulic actuator; an electronic control circuit coupled to and responsive to the front suspension sensor, the at least one load sensor, the hitch position sensor, and configured to drive the hitch control valve to control the flow of pressurized hydraulic fluid to the hitch hydraulic actuator in real time to reduce tractor pitching.
The electronic control circuit may include at least one feedback control circuit configured to automatically, periodically, and repeatedly receive the signals of the front suspension sensor, the at least one load sensor and the hitch position sensor, to combine the signals, to generate a valve control signal therefrom, and to apply the valve control signal to the hitch control valve (or valves) to vary a degree of opening of the hitch control valve (or valves).
The electronic control circuit may be configured to sample the signals of the front suspension sensor, the at least one load sensor and the hitch position sensor at least once every 50 milliseconds and to generate the valve control signal at least once every 50 milliseconds, more preferably at least every 20 milliseconds, and even more preferably, at least every 10 milliseconds.
The tractor may include at least one front suspension hydraulic control valve coupled to and between the pump and the at least one front suspension hydraulic actuator to control the height of the front suspension, and further wherein the front suspension hydraulic control valve is coupled to and driven by the electronic control circuit.
The electronic control circuit may include a first digital microprocessor coupled to the front suspension control valve and the front suspension sensor; a second digital microprocessor coupled to the hitch position sensor and the at least one load sensor; and a CAN (controller area network) bus coupling the first and second digital microprocessors and configured to transmit the signal indicative of the position of the front suspension with respect to the chassis from the first digital microprocessor to the second digital microprocessor.
The second microprocessor may be coupled to the hitch control valve and configured to receive the signal indicative of the front position sensor over the CAN bus, to combine that signal with the hitch position sensor signal and the load sensor signal, to generate a valve control signal therefrom, and to apply the valve control signal to the hitch control valve to vary a degree of opening of the hitch control valve.
In accordance with a second embodiment of the invention, a method of electronically reducing pitching in a tractor is provided, including the steps of (a) receiving an electrical signal from a front suspension sensor indicating the position of a front suspension; (b) receiving an electrical signal from a hitch position sensor indicating the height of a hitch with respect to a chassis; (c) receiving an electrical signal from at least one load sensor indicative of a load experienced by the hitch; (d) combining the front suspension sensor signal, the hitch position sensor signal and the load sensor signal; (e) generating a hitch hydraulic actuator signal calculated to drive the hitch upward or downward with respect to the chassis; and (f) driving the hitch upward or downward with respect to the chassis to thereby reduce tractor pitching. These steps (a)-(f) may be automatically and repeatedly executed at least once every 50 milliseconds.
The method may include the step of transmitting the front suspension sensor signal from a first microprocessor coupled to the front suspension sensor to a second microprocessor, and the step of combining may include the step of combining the front suspension sensor signal, the hitch position sensor signal and the at least one load sensor signal in the second microprocessor.
The step of generating a hitch hydraulic actuator signal may include the step of generating the hydraulic actuator signal in the second microprocessor and applying the hydraulic actuator signal to a valve that is fluidly coupled to and between a hydraulic pump and a hitch hydraulic actuator to regulate a flow of hydraulic fluid from the pump to the actuator.
In accordance with a third embodiment of the invention, a work vehicle having a ride control system that controls vehicle pitching is provided, the vehicle including a chassis; an engine mounted on the chassis; a hydraulic pump coupled to and driven by the engine to provide a flow of pressurized hydraulic fluid; a front suspension including two front wheels disposed on opposing sides of the chassis and supported by at least one front suspension hydraulic actuator configured to raise and lower the two front wheels with respect to the chassis; a front suspension sensor coupled to the front suspension to generate a signal indicative of the position of the front suspension with respect to the chassis; two rear wheels coupled to the chassis to rotate with respect thereto and drive the vehicle over the ground; a hitch coupled to the rear of the chassis and configured to be coupled to an overhanging load extending from the chassis; a hitch position sensor coupled to the hitch to provide a signal indicative of an elevation of the hitch with respect to the chassis; a hitch hydraulic actuator coupled to the hitch to raise and lower the hitch with respect to the chassis; at least one load sensor coupled to the chassis to provide a signal indicative of a load on the hitch; at least one electrically actuated hitch control valve coupled to and between the pump and the hitch hydraulic actuator to regulate the flow of pressurized hydraulic fluid to the hitch hydraulic actuator; and an electronic control circuit coupled to and responsive to the front suspension sensor, the load sensor, the hitch position sensor, and the hitch control valve to control the flow of pressurized hydraulic fluid to the hitch hydraulic actuator in real time to reduce vehicle pitching.
The electronic control circuit may include at least one feedback control circuit configured to automatically, periodically, and repeatedly receive the signals of the front suspension sensor, the at least one load sensor and the hitch position sensor, to combine the signals, to generate a valve control signal therefrom, and to apply the valve control signal to the hitch control valve to vary a degree of opening of the hitch control valve.
The electronic control circuit may be configured to sample the signals of the front suspension sensor, the at least one load sensor and the hitch position sensor at least once every 50 milliseconds and to generate the valve control signal at least once every 50 milliseconds.
The work vehicle may include at least one front suspension hydraulic control valve coupled to and between the pump and the at least one front suspension hydraulic actuator to control the height of the front suspension, and further wherein the front suspension hydraulic control valve is coupled to and driven by the electronic control circuit.
The electronic control circuit may include a first digital microprocessor coupled to the front suspension control valve and the front suspension sensor; a second digital microprocessor coupled to the hitch position sensor and the at least one load sensor; and a CAN bus coupling the first and second digital microprocessors and configured to transmit the signal indicative of the position of the front suspension with respect to the chassis from the first digital microprocessor to the second digital microprocessor.
The electronic control circuit may be configured to sense a front suspension sensor signal indicative of the front wheels lifting off the ground and to lower the hitch responsively.
The signal indicative of the wheels lifting off the ground may be generated by the front suspension sensor signal using a dynamic model that predicts that the wheels will leave the ground.